Heretofore, there have been a multiplicity of multi-piece flat top containers. For example:
Scanga et al U.S. Pat. No. 4,094,460 discloses the broad idea of placing a sealing ring about the top of a container, with a foil membrane secured to the top surface of the ring by a peelable coating and permanently secured to the undersurface of an overcap. The sealing ring is heat sealed to an inner foil layer of the container.
Rutkowski U.S. Pat. No. 2,257,919 includes a sheet metal ring having an inner wall portion, an outer wall portion, with an intermediate pocket for mounting on the top edge of a container. A sheet metal closure or cover is adapted to mount on the upper edge seat of the ring, confining an optional packing disk therebetween.
Whitney U.S. Pat. No. 3,445,024 discloses a flexible sealing ring or gasket adapted to engage the top beaded edge of a glass container to seal same when covered by a cover member.
Strouse et al U.S. Pat. No. 3,396,899 includes a liner comprising a panel spanning the mouth of a container, with an annular flange having an inner wall, an outer wall, and an upper hot melt engaging section. A closure flange mounts on the latter section with a suitable adhesive therebetween.
Johnson et al U.S. Pat. No. 3,892,351 has a membrane type closure sealed by a seam to the top rolled-over edge of a round container. This, in turn is covered by an overcap with inner heat deforming ribs.
Edwards U.S. Pat. No. 4,787,530 discloses a container having a tamper-evident lid connected thereto by an inner airtight bead arrangement, with downward projections around the outer periphery of the container, and a continuous ring affixed to the downward projections.
A review of these prior art references discloses that none of them would be functional without their respective overcaps.